First you need to see if it is the motor that is bad. Usually you find the relay or switch that powers the motor and see if you have voltage.

It's good you want to fix it, but microwaves are better left to professionals. A novice could hurt themselves working on a microwave.

Nick

____________________" Giving numerical data to Sears management is like giving a monkey a machine gun. No one knows for certain what will happen, but you can be sure of two things... It will be real messy, and only the monkey will be unharmed"